Cold beam of isotopically pure Yb atoms by deflection using 1D-optical molasses

We demonstrate the generation of an isotopically pure beam of laser-cooled Yb atoms by deflection using 1D-optical molasses. Atoms in a collimated thermal beam are first slowed using a Zeeman slower. They are then subjected to a pair of molasses beams inclined at 45^° with respect to the slowed atomic beam. The slowed atoms are deflected and probed at a distance of 160 mm. We demonstrate the selective deflection of the bosonic isotope ¹⁷⁴Yb and the fermionic isotope ¹⁷¹Yb. Using a transient measurement after the molasses beams are turned on, we find a longitudinal temperature of 41 mK.     

Frequency locking of a 399-nm laser referenced to fluorescence spectrum of an ytterbium atomic beam

The laser cooling of ytterbium(Yb) atoms needs a 399-nm laser which operates on the strong1S0-1P1 transition and can be locked at the desired frequencies for different Yb isotopes.We demonstrate a frequency locking method using the fluorescence spectrum of an Yb atomic beam as a frequency reference.For unresolved fluorescence peaks,we make the spectrum of the even isotopes vanish by using the strong angular-dependence of the fluorescence radiations;the remained closely-spaced peaks are thus clearly resolved and able to serve as accurate frequency references.A computer-controlled servo system is used to lock the laser frequency to a single fluorescence peak of interest,and a frequency stability of 304 kHz is achieved.This frequency-locked laser enables us to realize stable blue magneto-optic-traps(MOT) for all abundant Yb isotopes.     

Magneto-Optical Trapping of Ytterbium Atoms with a 398.9nm Laser

We report the realization of ytterbium magneto-optical trap （MOT） operating on the dipole-allowed ^1S0 - ^1P1 transition at 398.9nm. The MOT is loaded by a slowed atomic beam produced by a Zeeman slower. All seven stable isotopes of Yb atoms could be trapped separately at different laser detuning values. Over 10^7 174 Yb atoms are collected in the MOT, whereas the atom number of fermionic isotope ^171Yb is roughly 2.3 × 10^6 due to a lower abundance. Without the Zeeman slower the trapped atom numbers are one order of magnitude lower. Both the even and odd isotopes are recognized as excellent candidates of optical clock transition, so the cooling and trapping of ytterbium atoms by the blue MOT is an important step for building an optical clock.     

Current Trends in Laser Separation of Isotopes in Monatomic Vapors

A comparative analysis of the techniques of laser isotope separation in monatomic vapors is presented. The restraints inherent in the conventional isotope separation technique AVLIS (atomic vapor laser isotope separation) are discussed as applied to the large-scale production of various isotopes. The requirements that should be met by the chemical reactions are formulated for the use of these reactions in isotope separation. The photochemical technique was shown to be quite competitive with the AVLIS.     

Optimization of feed flow parameters in separation of neodymium isotopes by atomic vapor selective laser photoionization and analysis of results

Experimental data for separation of neodymium isotopes by atomic vapor selective laser photoionization are analyzed. Atom scattering in the working volume and the Doppler shift of the atom absorption line are shown to be the basic deselecting processes in the experimental cell studied. A data processing technique that allows one to determine the effect of either deselecting process on the product enrichment and yield is suggested. The experimental dependence of the target isotope concentration in photoions present in the separating chamber on the angular divergence (collimation) of the atomic vapor flow along the laser beam is found. A method for determining the vapor flow optimal angular collimation is developed.     

Selective photochemical isotope “burning” upon the interaction of resonant laser radiation with atoms

The method of laser isotope separation based on selective excited-atom “burning” in a flow with buffer and reagent gases was implemented experimentally for zinc and rubidium. Selective excitation of isotopes was accomplished by the one-photon method using weak absorption lines and at the edge of the Doppler contour of atomic absorption with small isotope shift.     

A study of isotopically selective photoionization of ytterbium atoms for laser isotope separation

Atomic-vapor laser isotope separation (AVLIS) is studied experimentally and theoretically for ytterbium vapors. The optimum ionization scheme and the process dynamics are determined. The photoionization scheme uses the transitions $$6^1 S_0 \mathop \to \limits^{555.648nm} 6^3 P_1 \mathop \to \limits^{581.067nm} (7/2,3/2)_2 \mathop \to \limits^{582.79nm} (52353cm^{ - 1} ).$$ For a numerical study of photoionization dynamics, the mathematical model of the AVLIS process is used, which is based on the density matrix formalism and Maxwell's equations. Selective photoionization of the¹⁶⁸Yb isotope is simulated numerically. The yield and selectivity of the process are determined. It is shown that the length of the photoionization region is limited because the laser radiation is absorbed by atoms of¹⁷¹Yb and¹⁷³Yb isotopes. The advantage of the laser method over the method using an electromagnetic separator is demonstrated.     

Atomic beam,optogalvanic and stored ion spectroscopy for radioactive isotopes

Systematic studies of the optical isotope shift and the hyperfine splitting of long chains of stable and radioactive isotopes were performed. The method applied was laser induced resonance absorption; the experimental techniques were the atomic beam method with fluorescence detection and the optogalvanic method. The theory of hyperfine splitting and isotope shift of atoms is reviewed in short with emphasis on the aspects interesting for nuclear physics and on the evaluation problem. The experimental methods are described and their key parameters sensitivity and resolution are discussed. Preliminary results on stored thorium ions are given. Sample results for the nuclear quantity δ<r ²> derived from atomic beam experiments with tin and strontium are presented.     

Hyperfine structure and isotope shifts of neutron-rich138–146Cs

The 6s²S_1/2-7_p ²P_3/2 transition in^138–142Cs (λ=455.5 nm) has been investigated by high-resolution collinear laser spectroscopy in a fast atomic beam. The isotopes are obtained by on-line mass separation of fission products. Nuclear moments and changes of mean-square charge radii are derived from hyperfine structure and isotope shift.     

Multifrequency radiation pressure laser,isotope separation

Isotope separation by laser deflection of an atomic beam is limited in its efficiency by the accumulation of atoms in metastable states. This restriction can be removed with the use of lasers which excite metastable atoms to states from which spontaneous decay to the ground state is allowed. This is demonstrated in the separation of barium isotopes, where efficiency was improved from a lower limit of 70% to at least 83% using a second laser. Efficiency approaching 100% can be achieved in barium with a second laser but the required wavelength is not available.     

铬原子束横向一维激光冷却的蒙特卡罗方法仿真

激光汇聚铬原子沉积实验中,铬原子束准直度的好坏非常重要.利用蒙特卡罗随机思想选取原子轨迹初始条件,将⁵²Cr原子以外的其他同位素、纵向速度分布和横向发散角等因素综合考虑,对铬原子束横向一维激光冷却进行了优化分析.经过与均匀取值法比较,这种方法能够更好地体现原子运动的不确定性,挑选出不参与冷却过程的同位素,使考察界面内原子束的横向位置分布更好的符合实验结果.结果显示,冷却过程中其他同位素的存在使原子束横向位置分布的中心最大值减小9.3%,半高宽增加11%,并且增加轮廓曲线的基底. 关键词： 激光冷却 蒙特卡罗方法 铬原子束     

Doppler-dependent fluorescence spectroscopy of Yb atomic gas for trapped-ion experiments

An ion trap-based Quantum system has been one of the leading architectures toward building a scalable and practical quantum computer. The trapped ion system also has been used for precision experiments such as quantum sensing, metrology, and atomic clock. For the ion-trap experiment, searching resonant frequencies of atomic isotopes are essential for selectively ionization and trapping a specific isotope. In this work, we set up an Yb fluorescence spectroscopy for detecting 399 nm photons of ¹S₀ → ¹P₁ transition of the Yb gas from a heated oven. We observed the relative frequency differences between the Yb isotopes and calibrated an optical wavemeter comparing with previous literatures. In addition, we obtain characteristic properties of the atomic oven such as gas’ velocity and density distribution at different oven temperatures. Our experiment can offer a relatively simple and cost-efficient apparatus of spectroscopy and can be useful for designing trap devices in the trapped-ion experiment.     

Laser separation of rare isotopes in industrial-scale quantities

The series of investigations into laser isotope separation by the atomic vapor laser isotope separation (AVLIS) method, carried out at the Institute of General Physics of the Russian Academy of Sciences and the Scientific-Production Firm LAD in the last 4–5 years, is discussed. Basic physical problems solved in the development of facilities capable of producting high-enrichment¹⁶⁸Yb on an industrial scale are pointed out. Some units of the facility are briefly described, on which the following¹⁶⁸Yb concentrations are achieved: 90–95% in plasma, up to 62% on the collector, and up to 45% in wastes. The production rate of enriched ytterbium reaches 5–10 mg/h (more than a gram per month). Institute of General Physics of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 82–87, August, 1999.     

Accurate isotope shift measurements on short lived neon isotopes

We report on fast beam collinear laser spectroscopy measurements that demonstrate the feasibility of accurate isotope shift measurements for short lived Ne isotopes including the proton halo candidate ¹⁷Ne. Ultra high sensitivity is achieved by the application of an efficient resonance detection scheme based on collisional ionization and ion counting via the β decay. A direct measurement of the kinetic energy of the atomic Ne beam provides the required high accuracy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Isotope shift and hyperfine structure measurements for 155Yb by laser ion source technique

The change in the mean square charge radius and electromagnetic moments of the neutron deficient ¹⁵⁵Yb isotope have been determined using resonance ionization spectroscopy in a laser ion source. The data point to an absence of a marked deformation change for Yb isotopes with N=84−86. Received: 2 October 1997 / Revised version: 24 October 1997     

Laser Spectroscopy Programme at the Jyväskylä IGISOL

This paper reviews the status of the laser spectroscopy programme being carried using the IGISOL mass separator in combination with an RFQ cooler-buncher. Measurements in the zirconium region are being extended to the yttrium isotopes. Two K = 8 isomers, in ¹⁷⁶Yb and ¹³⁰Ba, are found to have smaller mean square charge radii than their ground states, and the isotope shifts of stable osmium isotopes have been measured off-line by collinear laser spectroscopy.     

An injection-seeded high-repetition rate Ti:Sapphire laser for high-resolution spectroscopy and trace analysis of rare isotopes

An injection-seeded high-repetition rate (～10 kHz) Ti:sapphire laser with a spectral bandwidth of ～20 MHz and an average output power of above 1.5 W has been developed. We report on its demonstration and characteristics with respect to the spectral, temporal, and spatial properties as well as the output energy. In crossed-beam resonance ionization on a well-collimated thermal atomic beam, the ～200 MHz hyperfine structure of the D₂ transition at 308 nm of ²⁷Al has been well resolved. Applications of the system in the field of insource laser spectroscopy for on-line produced short-lived radioactive isotopes as well as for selective-trace isotope determination are discussed.     

A novel method to measure the isotope shifts and hyperfine splittings of all ytterbium isotopes for a 399-nm transition

We report the experimental results on measuring the isotope shifts and hyperfine splittings of all ytterbium isotopes for a 399-nm transition by using a quite simple and novel method.It benefits from the advantages of the modulation transfer spectroscopy in an ytterbium hollow cathode lamp and the Doppler-free spectroscopy in a collimated ytterbium atomic beam.The key technique in this experiment is simultaneously measuring the frequency separations of the two spectra twice,and the separation difference between two measurements is solely determined by the well-defined frequency of an acousto-optics modulator.Compared with the most of previously reported experimental results,ours are more accurate and completed,which will provide the useful information for developing a more accurate theoretical model to describe the interaction inside an ytterbium atom.     

钕离子同位素移位和超精细结构光谱

原子光谱中,同位素移位和超精细结构光谱是少数几个能够将原子物理和原子核物理这两个不同的物理分支联系起来的课题之一.利用共线快离子束-激光光谱学方法测量了单电荷态钕离子4f45d6G3/2→(26041)°5/2跃迁(波长577.21 nm)的共振光谱,得到了所有7个稳定同位素(A=142～146,148,150)之间的能量移位和2个奇同位素(A=143,145)的超精细结构光谱.     

Hyperfine structure and isotope shift of highly excited barium-I states

High-resolution laser-spectroscopy measurements of hyperfine structure and isotope shifts were performed for the 6snd ¹ D ₂ sequence of Ba-I in the regionn=12–24. Stepwise laser excitations of a collimated atomic beam were used. A strong influence on the hyperfine structure is observed at the perturbation atn=14, caused by interaction with the 5d7d configuration. Whereas the isotope shift for the even isotopes stays essentially constant with increasingn, the odd isotopes exhibit a strong change, indicating hyperfine-induced shifts.